No abstract

To investigate the position and amount of the CF 3 group affecting the coloration of polyimides (PIs), we prepared 2,2-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]hexafluoropropane (2) with four CF 3 groups with 2-chloro-5-nitrobenzotrifluoride and 2,2-bis(4-hydroxyphenol)hexafluoropropane. A series of soluble and lightcolored fluorinated PIs (5) were synthesized from 2 and various aromatic dianhydrides (3a-3f). 5a-5f had inherent viscosities ranging from 0.80 to 1.19 dL/g and were soluble in amide polar solvents and even in less polar solvents. The glass-transition temperatures of 5 were 221-265°C, and the 10% weight-loss temperatures were above 493°C. Their films had cutoff wavelengths between 343 and 390 nm, b* values (a yellowness index) ranging from 5 to 41, dielectric constants of 2.68 -3.01 (1 MHz), and moisture absorptions of 0.03-0.29 wt %. In a comparison of the PI series 6-8 based on 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]propane, and 2,2-bis[4-(4-aminophenoxy)phenyl]propane, we found that the CF 3 group close to the imide group was more effective in lowering the color; this means that CF 3 of 5, 7, and 8f was more effective than that of 6c. The color intensity of the four PI series was lowered in the following order: 5 Ͼ 7 Ͼ 6 Ͼ 8. The PI 5f, synthesized from diamine 2 and 4,4Ј-hexafluoroisopropylidenediphthalic anhydride, had six CF 3 groups in a repeated segment, so it exhibited the lightest color among the four series.

No abstract

A novel fluorinated diamine monomer, 2,2-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]propane (2), was prepared through the nucleophilic substitution reaction of 2-chloro-5-nitrobenzotrifluoride with 2,2-bis(4-hydroxyphenyl)propane in the presence of potassium carbonate, followed by catalytic reduction with hydrazine and Pd/C. Polyimides were synthesized from diamine 2 and various aromatic dianhydrides 3a-f via thermal imidization. These polymers had inherent viscosities ranging from 0.73 to 1.29 dL/g. Polyimides 5a-f were soluble in amide polar solvents and even in less polar solvents. These films had tensile strengths of 87-100 MPa, elongations to break of 8 -29%, and initial moduli of 1.7-2.2 GPa. The glass transition temperatures (T g ) of 5a-f were in the range of 222-271°C, and the 10% weight loss temperatures

A se ries of sol u ble flu o ri nated poly amides (4a-h) were syn the sized from 2-trifluoromethyl-4,4diaminodiphenylether (2) with var i ous ar o matic diacids (3a-c) and imide-containing diacids (3d-h) via di rect polycondensation with triphenyl phosphite and pyridine. Diamine 2 was pre pared through nucleophilic substi tu tion re ac tion of 2-chloro-5-nitrobenzotrifluoride and 4-nitrophenol in the pres ence of an hy drous K2CO3 to yield the dinitro com pound, fol lowed by cat a lytic re duc tion with hydrazine and Pd/C. These poly mers had in her ent vis cos i ties rang ing from 0.85 to 1.12 dL/g. All of the poly amides were sol u ble in aprotic po lar solvents such as NMP, DMAc, DMF, and DMSO. Poly mer films 4a-h had ten sile strengths of 77-95 MPa, elonga tions to break of 8-40%, and ini tial moduli of 1.6-2.2 GPa. The glass tran si tion tem per a tures of these polymers were in the range of 235-268 C, and the amount of car bon ized res i dues of the poly mers at 800 °C in nitro gen at mo sphere were above 52%.